Flow rate estimation method of blood pump

ABSTRACT

In a flow rate estimation method of a blood pump, a general flow rate estimation formula which includes a correction term is formed based on a plurality of blood pumps. Measured data obtained from an objective blood pump implanted inside a patient is substituted into the correction term, thus forming a flow rate estimation formula of the objective blood pump. The flow rate Q of the objective blood pump is estimated based on the flow rate estimation formula and the values of the rotational speed N and the consumption current I of the motor of the objective blood pump, and the attribute data Z of the blood of the patient.

TECHNICAL FIELD

The present invention relates to a flow rate estimation method of ablood pump, a flow rate estimation device of a blood pump, a blood pumpsystem, and a storage medium.

BACKGROUND OF THE INVENTION

As one of medical treatments for curing a serious heart disease patient,treatment which uses an implantable blood pump has been performed. Toappropriately perform the treatment, it is necessary to accurately finda flow rate of the blood pump. Accordingly, a blood flow meter such as ablood flow meter based on a thermodilution method, a blood flow meterbased on a dye dilution method, an electromagnetic blood flow meter, anultrasonic blood flow meter, a blood flow meter based on atransesophageal echocardiography, a blood flow meter based on atransthoracic echocardiography or a blood flow meter based on anelectric impedance method is mounted inside or outside a body of apatient, and the flow rate of the implantable blood pump is measured.

However, with respect to the blood flow meter such as the blood flowmeter based on the thermodilution method, the blood flow meter based onthe dye dilution method, the electromagnetic blood flow meter or theultrasonic blood flow meter, it is necessary to mount such a blood flowmeter inside the body of the patient, and hence, the use of the bloodflow meter is considerably invasive to the patient. Accordingly, themounting of the blood flow meter inside the body of the patient islimited for a certain period postoperatively in an actual use, andhence, after removing the blood flow meter from the body of the patient,a method which allows a user to know the flow rate of the blood pumpwithout using the blood flow meter becomes necessary.

In addition, with respect to the blood flow meter such as the blood flowmeter based on the transesophageal echocardiography, the blood flowmeter based on the transthoracic echocardiography or the blood flowmeter based on the electric impedance method, steps for measuring theflow rate of blood are cumbersome in an actual operation, and hence, itis also fairly invasive to the patient. Accordingly, a method whichallows a user to know the flow rate of the blood pump without using theblood flow meter also becomes necessary.

FIG. 14 and FIG. 15 are views for explaining a conventional blood pumpsystem which satisfies such demands as mentioned above.

The conventional blood pump system 901 includes, as shown in FIG. 14 andFIG. 15, a blood pump 905 which discharges blood by rotating an impeller921 by making use of a rotational force of a motor 934 as a drivingpower source, aviscosity/rotational-speed/motor-current/discharge-flow-rate relateddata storing part 960 which stores “predetermined viscosity-relateddischarge-flow-rate data” which is constituted of various motorcurrent/discharge flow rate related data at various different impellerrotational speeds under a predetermined liquid viscosity with respect tovarious different predetermined viscosities, a blood parameter inputpart 957, a sensor circuit 955 which has a function of measuring andcalculating an impeller rotational speed which measures the rotationalspeed of the impeller 921, a motor current measuring part which has afunction of measuring a current supplied to the motor 934, and adischarge flow rate arithmetic calculation part 958 which calculates aliquid discharge flow rate based on liquid viscosity, a motor currentand an impeller rotational speed using the liquid viscosity, theimpeller rotational speed, the motor current, and viscosity/rotationalspeed/motor current/discharge flow rate related data (for predeterminedviscosity-related discharge-flow-rate data table, see FIG. 15).

According to the blood pump system 901, as shown in FIG. 14 and FIG. 15,since the impeller rotational speed, the motor current and the bloodviscosity are measured and, thereafter, a blood discharge flow rate iscalculated based on the measured values and the predeterminedviscosity-related discharge-flow-rate data table, the flow rate of theblood pump can be estimated without using any blood flow meter.

Further, according to the blood pump system 901, as shown in FIG. 14 andFIG. 15, since the blood discharge flow rate is calculated based on thepredetermined viscosity-related discharge-flow-rate data table, that is,the minimal number of individual data which satisfies the requiredaccuracy is stored as a data table and the blood discharge flow rate iscalculated selectively using the data close to a current value to becalculated or the like, the accurate flow rate can be easily obtained incomparison with a case that the blood discharge flow rate is calculatedbased on a relationship formula of the impeller rotational speed, themotor current, the blood viscosity, and the flow rate of the blood pump(see patent document 1, for example).

[Patent document 1]

JP-A-2003-210572

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, in case of implantable blood pumps, it is not easy to eliminatethe individual difference of a blood pump property because oflimitations on the structure. Accordingly, when the flow rate of theblood pump is estimated using the above-mentioned method according tothe conventional blood pump system 901, the estimation accuracy of theflow rate of each blood pump is lowered due to the individual differenceof the blood pump property, and hence, there arises a drawback that themedical treatment which uses the implantable blood pump cannot beproperly performed.

Accordingly, the present invention has been made to overcome such adrawback, and it is an object of the present invention to provide a flowrate estimation method of a blood pump and a flow rate estimation deviceof a blood pump, which can effectively suppress the lowering of accuracyof a flow rate estimation result attributed to the individual differenceof the blood pump property. It is another object of the presentinvention to provide a blood pump system which includes such a flowrateestimation device of a blood pump. It is still another object of thepresent invention to provide a storage medium which is necessary forrealizing such a flow rate estimation device of a blood pump.

Means for Solving the Problems

(1) A flow rate estimation method of a blood pump according to thepresent invention is a method which estimates a flow rate Q of the bloodpump which discharges blood using a rotational force of a motor as adriving power source based on a rotational speed N of the motor, aconsumption current I of the motor and an attribute data Z of blood of apatient, and is characterized in that the flow rate estimation method ofa blood pump includes a first step which forms flow rate estimationinformation which describes the relationship among the rotational speedof the motor, the consumption current of the motor and the flow rate ofan objective blood pump or a blood pump for flow rate estimation, andthe attribute data of a liquid, and a second step which estimates theflow rate Q of the blood pump based on the flow rate estimationinformation and the values of N, I and Z which are obtained by measuringthe rotational speed N of the motor and the consumption current I of themotor in the objective blood pump which is implanted inside the body ofthe patient and the attribute data Z of the blood of the patient.

According to the flow rate estimation method of a blood pump of thepresent invention, the flow rate estimation information is formed forevery objective blood pump on which the flow rate estimation isperformed in the first step, and the flow rate estimation is performedon the objective blood pump based on the flow rate estimationinformation in the second step, and hence, there is no deterioration ofaccuracy of the flow rate estimation result attributed to the individualdifference of the characteristic of the blood pump, thus achieving theobject of the present invention.

In the flow rate estimation method of a blood pump of the presentinvention, “objective blood pump” implies a blood pump on which the flowrate estimation is performed.

Further, “a plurality of blood pumps” described later implies aplurality of arbitrary blood pumps on which the property (such asgeneral flow rate estimation information or the like explained later) ofthe blood pumps are measured and evaluated out of the blood pumps havingthe same standard and specification as the “objective blood pump”.

Further, in the flow rate estimation method of a blood pump of thepresent invention, “liquid” indicates liquid which flows in the bloodpump at forming the flow rate estimation information and may be either“test liquid” or “blood of patient”.

(2) In the flow rate estimation method of a blood pump as mentioned inthe above (1), the flow rate estimation information may be a flow rateestimation formula.

By adopting such a method, by substituting the value of the rotationalspeed N of the motor, the consumption current I of the motor and theattribute data Z of the blood of the patient which are measured in thesecond step in the flow rate estimation formula, it becomes possible toeasily perform the flow rate estimation of the blood pump.

(3) In the flow rate estimation method of a blood pump as mentioned inthe above (1), the flow rate estimation information may be a flow rateestimation table.

By adopting such a method, it is possible to easily perform the flowrate estimation of the blood pump by selectively referring to portionsof the flow rate estimation table which approximate the rotational speedN of the motor, the consumption current I of the motor and the attributedata Z of the blood of the patient which are measured in the second stepand, at the same time, performing a proper complementary calculation.

(4) In the flow rate estimation method of a blood pump as mentioned inthe above (1), the first step may be a step which forms the flow rateestimation information by measuring the actual flow rate of theobjective blood pump using a blood flow meter when the rotational speedof the motor and the consumption current of the motor in the objectiveblood pump and the attribute data of the test liquid are respectivelychanged.

The step for forming the flow rate estimation information is cumbersomein general, and hence requires considerable time and procedure. This isbecause that the formation of the flow rate estimation informationrequires the measurement of the flow rate of the blood pump byrespectively changing the rotational speed of the motor, the consumptioncurrent of the motor and the attribute data of the liquid.

However, according to the flow rate estimation method of the blood pumpdescribed in the above (4), the flow rate estimation information isformed using the test liquid, and hence, it is possible to finish such acumbersome and time-consuming first step before shipping in advance.

Further, it is possible to perform such a cumbersome and time-consumingfirst step before implanting the obj ective blood pump into a body of apatient, and hence, there is no possibility that a burden imposed on thepatient is increased.

Still further, by performing the formation of the flow rate estimationinformation for every objective blood pump beforehand, immediately afterimplanting the objective blood pump inside the body of the patient, itis possible to accurately perform the flow rate estimation with respectto the objective blood pump.

(5) In the flow rate estimation method of a blood pump as mentioned inthe above (1), the first step may include a step which forms generalflow rate estimation information including correction information bymeasuring flow rates of blood pumps using a blood flow meter when therotational speeds of the motors and the consumption currents of themotors in a plurality of respective blood pumps, and the attribute dataof a test liquid are respectively changed, and a step in which therotational speed of the motor and the consumption current of the motorin the objective blood pump, and the attribute data of the test liquidare measured, and the flow rate of the blood pump is measured using theflow meter, and the flow rate estimation information on the objectiveblood pump is formed based on the general flow rate estimationinformation by substituting the obtained measured data into thecorrection information.

By adopting such a method, in the same manner as the case of the flowrate estimation method of a blood pump described in the above (4), theflow rate estimation information is formed using the test liquid, andhence, it becomes possible to finish such a cumbersome andtime-consuming first step before shipping in advance.

Further, since such a cumbersome and time-consuming first step can beperformed before implanting the objective blood pump inside the body ofthe patient, there is no possibility that a burden imposed on a patientis increased.

Still further, by performing the formation of the flow rate estimationinformation for every objective blood pump beforehand, immediately afterimplanting the objective blood pump inside the body of the patient, itbecomes possible to accurately perform the flow rate estimation withrespect to the objective blood pump.

Further, in the flow rate estimation method of the blood pump describedin the above (5), the formation of the flow rate estimation informationwhich is originally cumbersome and time-consuming is divided into theformer step which forms the general flow rate estimation informationincluding the correction information and the latter step which forms theflow rate estimation information on the objective blood pump based onthe general flow rate estimation information by substituting themeasured data obtained for every objective blood pump into thecorrection information, wherein among these steps, the former step whichis originally cumbersome and time-consuming is performed preliminarilyusing a plurality of blood pumps, and the latter step which isrelatively less time-consuming (unnecessary to perform measurement byrespectively changing the rotational speed of the motor, the consumptioncurrent of the motor and the attribute data of the test liquid differentfrom the former step) is performed using the objective blood pump,whereby it becomes possible to further easily form the flow rateestimation information as a whole compared to the flow rate estimationmethod of the blood pump described in the above (4).

Here, while the general flow rate estimation information including thecorrection information is the information necessary for forming flowrate estimation information, the general flow rate estimationinformation per se includes the correction information which has yet anindeterminate term, and hence, even when the measured data on therotational speed N of the motor and the consumption current I of themotor of the objective blood pump which is implanted inside the body ofthe patient, and the attribute data Z of the blood of the patient issubstituted into the general flow rate estimation information, the flowrate cannot be estimated.

(6) In the flow rate estimation method of a blood pump as mentioned inthe above (1), the first step may includes a step which forms generalflow rate estimation information including correction information bymeasuring flow rates of blood pumps using a blood flow meter when therotational speed of the motor and the consumption current of the motorin a plurality of respective blood pumps, and the attribute data of atest liquid are respectively changed, and a step in which the rotationalspeed of the motor and the consumption current of the motor in theobjective blood pump which is implanted inside the body of the patient,and the attribute data of the blood of the patient are measured and, theflow rate of the blood pump is measured using the blood flow meter, andthe flow rate estimation information on the objective blood pump isformed based on the general flow rate estimation information bysubstituting the obtained measured data into the correction information.

By adopting such a method, in the same manner as the case of the flowrate estimation method of a blood pump described in the above (5), theformation of the flow rate estimation information which is originallycumbersome and time-consuming is divided into the former step whichforms the general flow rate estimation information per se including thecorrection information and the latter step which forms the flow rateestimation information on the objective blood pump based on the generalflow rate estimation information by substituting the measured dataobtained from every objective blood pump into the correctioninformation, wherein among these steps, the former step which isoriginally cumbersome and time-consuming is preliminarily performedusing the plurality of blood pumps, and the latter step which isrelatively less time-consuming is performed using the objective bloodpump, and hence, in the same manner as the case of the flow rateestimation method of the blood pump described in the above (5), itbecomes possible to easily form the flow rate estimation information asa whole.

Further, according to the flow rate estimation method of a blood pumpdescribed in the above (6), the flow rate estimation information on theobjective blood pump is formed based on the general flow rate estimationinformation by substituting the measured data obtained using theobjective blood pump which is implanted inside the body of the patientinto the correction information, and hence, the flow rate estimationinformation is formed on the objective blood pump under an environmentwhere it is actually used, whereby it is possible to effectivelysuppress the deterioration of the accuracy of the flow rate estimationresult due to the difference of the environment where the blood pump isused.

Further, according to the flow rate estimation method of a blood pumpdescribed in the above (6), the flowrate estimation information on theobjective blood pump is formed based on the general flow rate estimationinformation by substituting the measured data obtained using theobjective blood pump which is implanted inside the body of the actualpatient into the correction information and, thereafter, the flowrateestimation on the objective blood pump can be performed based on theflow rate estimation information. Accordingly, it becomes possible toeffectively suppress the deterioration of the accuracy of the flow rateestimation result attributed to a change of the property of the bloodpump along with a lapse of time.

Here, while the general flow rate estimation information including thecorrection information is, as also explained in the above (5), theinformation necessary for forming flow rate estimation information, thegeneral flow rate estimation information per se includes the correctioninformation which has yet an indeterminate term, and hence, even whenthe measured data on the rotational speed N of the motor and theconsumption current I of the motor of the objective blood pump which isimplanted inside the body of the patient, and the attribute data Z ofthe blood of the patient is substituted into the general flow rateestimation information, the flow rate cannot be estimated.

(7) In the flow rate estimation method of a blood pump as mentioned inthe above (6), the blood flow meter may be a blood flow meter based on athermodilution method, a blood flow meter based on a dye dilutionmethod, an electromagnetic blood flow meter, an ultrasonic blood flowmeter, a blood flow meter based on a transesophageal echocardiography, ablood flow meter based on a transthoracic echocardiography or a bloodflow meter based on an electric impedance method may be used.

With the use of such a blood flow meter, the flow rate of the objectiveblood pump which is implanted inside the body of the patient can bemeasured, thus realizing the flow rate estimation of the blood pump withhigher accuracy.

(8) In the flow rate estimation method of a blood pump as mentioned inthe above (6), in the estimation of a flow rate of the blood pump in thesecond step, when the measurement of the flow rate of the objectiveblood pump with use of the blood flow meter is allowable, the flow rateestimation information on the objective blood pump may be updated bymeasuring the flow rate of the blood pump using the blood flow meter inperforming the second step.

By adopting such a method, even when the property of the blood pump ischanged along with a lapse of time, it becomes possible to properlyupdate the flow rate estimation information to the newest flow rateestimation information, and hence, it becomes possible to furthereffectively suppress the deterioration of the accuracy of the flow rateestimation result attributed to a change of a property of the blood pumpalong with a lapse of time.

(9) In the flow rate estimation method of a blood pump as mentioned inany one of the above (5) to (8), the motor may particularly preferablybe a DC motor.

In the DC motor, a relationship that the consumption current I and ashaft torque of the motor are proportional to each other is established.Further, a linear relationship is established between the flow rate Q ofthe blood pump and the shaft torque. Accordingly, a linear relationshipis established between the flow rate Q of the blood pump and theconsumption current I of the motor, thus facilitating the completion ofthe flow rate estimation information on the objective blood pump basedon the general flow rate estimation information including the correctioninformation.

(10) In the flow rate estimation method of a blood pump as mentioned inthe above (1), the attribute data of the liquid, a test liquid or theblood of the patient may be constituted of viscosity and density of theliquid, the test liquid or the blood of the patient.

By adopting such a method, compared to a case in which only either oneof viscosity or density is adopted as the attribute data of the liquid,the test liquid or the blood of the patient, it is possible to realizethe flow rate estimation of the blood pump with higher accuracy.

(11) In the flow rate estimation method of a blood pump as mentioned inthe above (10), “a hematocrit value of the blood of the patient” may bemeasured in the second step in place of measuring “viscosity and densityof the blood of the patient”, and the flow rate of the blood pump may beestimated using “converted viscosity and converted density” which areobtained by conversion based on a hematocrit value of the blood of thepatient.

By adopting such a method, it is possible to perform the flow rateestimation of the blood pump using a simple method which only measuresthe hematocrit value without measuring viscosity or density of the bloodof the patient.

(12) In the flow rate estimation method of a blood pump as mentioned inthe above (1), the blood pump may particularly preferably be a bloodpump which has a mechanical seal part for performing shaft-sealing of arotational shaft of the motor.

In the blood pump having the mechanical seal part for performing theshaft-sealing of the rotational shaft of the motor (that is, forensuring sealing between the pump part and the drive part) in thismanner, the pump part and the drive part are well sealed from each otherslidably, and hence, leaking of the blood into the drive part from thepump part can be suppressed as much as possible thus suppressing thegeneration of blood clot, whereby stopping of the blood pump or a changeof an operational state of the blood pump can be suppressed as much aspossible.

On the other hand, such a mechanical seal part requires thepredetermined thrust load. Since there exists the relatively largeindividual difference with respect to this thrust load, there exists therelatively large individual difference also with respect to the propertyof the blood pump.

However, according to the flow rate estimation method of a blood pump ofthe present invention, the flow rate estimation information is formedfor every blood pump, and hence, even when the relatively largeindividual difference exists with respect to the property of the bloodpump, it is possible to eliminate the influence attributed to suchindividual difference, whereby it becomes possible to effectivelysuppress the deterioration of the accuracy of a result of the flow rateestimation attributed to the individual difference of the property ofthe blood pump.

Further, in such a mechanical seal part, the thrust load which isactually applied to a slide surface is relatively largely fluctuated dueto an environment in which the blood pump is used such as the posture ofthe motor, and hence, the property of the blood pump is also relativelyfluctuated.

However, according to the flow rate estimation method of a blood pumpdescribed in the above (6) of the present invention, the flow rateestimation information on the objective blood pump is formed based onthe general flow rate estimation information by substituting themeasured data obtained based on the objective blood pump which isimplanted inside the body of the patient into the correctioninformation, and hence, even when the property of the blood pump isrelatively largely fluctuated due to the environment in which the bloodpump is used, it is possible to effectively suppress the influenceattributed to the fluctuation of the property of the blood pump, wherebyit is possible to effectively suppress the deterioration of the accuracyof a result of the flow rate estimation attributed to the fluctuation ofthe property of the blood pump due to the environment in which the bloodpump is used.

Further, the mechanical seal part includes the slide surface whose slideproperty is largely changed along with a lapse of time, and hence, theproperty of the blood pump is also largely changed along with a lapse oftime.

However, according to the flow rate estimation method of a blood pumpdescribed in the above (6) of the present invention, the flow rateestimation information on the objective blood pump is formed based onthe general flow rate estimation information by substituting themeasured data obtained based on the objective blood pump which isimplanted inside the body of the patient into the correctioninformation, and hence, even when the property of the blood pump isrelatively largely changed along with a lapse of time, it is possible toeffectively suppress the influence attributed to the change of theproperty of the blood pump along with a lapse of time whereby it ispossible to effectively suppress the deterioration of the accuracy of aresult of the flow rate estimation attributed to the change of theproperty of the blood pump along with a lapse of time.

(13) A flow rate estimation method of a blood pump of the presentinvention estimates a flow rate Q of a blood pump which discharges bloodusing a rotational force of a motor as a driving power source based on arotational speed N of the motor, a consumption current I of the motorand an attribute data Z of blood of a patient, and is characterized inthat the rotational speed N of the motor and the consumption current Iof the motor of the objective blood pump which is implanted inside thebody of the patient, and the attribute data Z of the blood of thepatient are measured, and a flow rate Q of the blood pump is estimatedbased on a preliminarily formed flow rate estimation information on theobjective blood pump and the values of N, I and Z.

In this manner, according to the flow rate estimation method of a bloodpump of the present invention, the rotational speed N of the motor andthe consumption current I of the motor of the objective blood pump whichis implanted inside the body of the patient, and the attribute data Z ofthe blood of the patient are measured, and the flow rate Q of the bloodpump is estimated based on the preliminarily formed flow rate estimationinformation on the objective blood pump and these values N, I and Z, andhence, the deterioration of the accuracy of a result of the flow rateestimation attributed to the individual difference of the property ofthe blood pump can be eliminated thus achieving the object of thepresent invention.

(14) A flow rate estimation device of a blood pump of the presentinvention includes a function of estimating a flow rate of the bloodpump by the flow rate estimation method of the blood pump as mentionedin the above (1) or (13), and is characterized in that the flow rateestimation device of the blood pump includes a flow rate estimationinformation storing part which stores the flow rate estimationinformation on the objective blood pump, and a flow rate estimation partwhich estimates the flow rate Q of the blood pump based on the flow rateestimation information stored in the flow rate estimation informationstoring part using the rotational speed N of the motor, the consumptioncurrent I of the motor and the attribute data Z of the blood of thepatient.

In this manner, according to the flow rate estimation device of theblood pump of the present invention, the flow rate Q of the blood pumpcan be estimated based on the flow rate estimation information on theobjective blood pump which is stored in the flow rate estimationinformation storing part using the rotational speed N of the motor, theconsumption current I of the motor and attribute data Z of the blood ofthe patient, and hence, the deterioration of the accuracy of a result ofthe flow rate estimation attributed to the individual difference of theproperty of the blood pump can be eliminated thus achieving the objectof the present invention.

(15) A blood pump system of the present invention includes a blood pumpwhich discharges blood using a rotational force of a motor as a drivingpower source and an external controller which controls an operation ofthe blood pump, and is characterized in that the blood pump systemfurther includes the flow rate estimation device of the blood pump asmentioned in the above (14).

In this manner, according to the blood pump system of the presentinvention, with the provision of the above-mentioned excellent flow rateestimation device of a blood pump, the deterioration of the accuracy ofthe flow rate estimation result attributed to the individual differenceof the property of the blood pump can be eliminated, thus achieving theobject of the present invention.

(16) A storage medium of the present invention is used for the flow rateestimation device of the blood pump as mentioned in the above (14), andis characterized in that the storage medium stores the general flow rateestimation information including the correction information or the flowrate estimation information.

In this manner, according to the present invention, with the provisionof the storage medium, it becomes possible to realize theabove-mentioned excellent flow rate estimation device of the blood pump,and hence, the deterioration of the accuracy of the flow rate estimationresult attributed to the individual difference of the property of theblood pump can be eliminated, thus achieving the object of the presentinvention.

BRIEF EXPLANATION OF DRAWINGS

FIG. 1 is a cross-sectional view showing a blood pump;

FIG. 2 is a view for explaining a blood pump system according to anembodiment 1;

FIG. 3 is a view for explaining a flow rate estimation method of a bloodpump according to the embodiment 1;

FIG. 4 is a view showing a relationship between a flow coefficient and aconverted current for every rotational speed of a motor;

FIG. 5 is a view showing the difference between the objective blood pumpand an arbitrary blood pump with respect to a consumption current of themotor when a flow rate of a blood pump is changed for every rotationalspeed of the motor;

FIG. 6 is a view showing the difference (ratio) between the objectiveblood pump and an arbitrary blood pump with respect to a consumptioncurrent of the motor when the rotational speed of the motor is changed;

FIG. 7 is a view showing the difference between an estimated flow rateand a measured flow rate of the objective blood pump;

FIG. 8 is a view showing a relationship between a hematocrit value andviscosity of blood;

FIG. 9 is a view showing a relationship between a hematocrit value anddensity of blood;

FIG. 10 is a view for explaining a blood pump system according to anembodiment 2;

FIG. 11 is a view for explaining a flow rate estimation method of ablood pump according to the embodiment 2;

FIG. 12 is a view for explaining a blood pump system according to anembodiment 3;

FIG. 13 is a view for explaining a flow rate estimation method of ablood pump according to the embodiment 3;

FIG. 14 is a view for explaining a conventional blood pump system; and

FIG. 15 is a view for explaining a flow rate estimation method of theconventional blood pump.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the explanation is made with respect to a flow rateestimation method of a blood pump, a flow rate estimation device of ablood pump, a blood pump system and a storage medium to which thepresent invention is applied in conjunction with embodiments shown indrawings.

First of all, prior to the explanation of the respective embodiments ofthe present invention, a blood pump which is used in respectiveembodiments of the present invention is explained in conjunction withFIG. 1.

FIG. 1 is a cross-sectional view showing the blood pump used in therespective embodiments of the present invention. The blood pump 10includes, as shown in FIG. 1, a drive part 11 which has a cylindricalmotor and a pump part 12 which is connected to the drive part 11. Thepump part 12 includes an impeller 13 which is driven by way of a rotaryshaft of the motor, and a pump casing 14 which is connected to the drivepart 11 in a state that the pump casing 14 covers the impeller 13. Bloodinside a left ventricle of a heart of a human body flows inside the pumpcasing 14 via an artificial blood vessel and an inlet port 15 and, afterbeing imparted flow energy by the impeller 13, flows out to an aorta viaan outlet port 16 formed in a side surface of the pump casing 14 and anartificial blood vessel.

In such a blood pump 10, a mechanical seal part 17 is arranged betweenthe drive part 11 and the pump part 12. Accordingly, in the blood pump10, the pump part 12 and the drive part 11 are slidably and favorablysealed from each other thus suppressing leaking of the blood from thepump part 12 to the drive part 11 as much as possible. As a result, thegeneration of a blood clot is suppressed as much as possible thussuppressing stopping of the blood pump and a change in an operationstate of the blood pump as much as possible.

On the other hand, since the blood pump 10 is provided with themechanical seal part 17, there exists the large individual difference,the large dependency on usage environment and a large change along witha lapse of time with respect to the property of the blood pump 10. Inthis manner, it is not easy to accurately perform the flow rateestimation of the blood pump 10. Accordingly, to properly perform thetreatment of a serious heart disease using such a blood pump 10, a flowrate estimation method of a blood pump which can accurately perform theflow rate estimation of the blood pump is particularly stronglyrequested.

In the respective embodiments, as such a blood pump 10, a centrifugalblood pump which can ensure a larger blood flow rate compared to anaxial blood flow motor is used. Further, in the respective embodiments,a DC motor is used as the motor for driving the impeller 13 of the bloodpump 10.

EMBODIMENT 1

The embodiment 1 is an embodiment with respect to the flow rateestimation method of a blood pump described in claim 6 of the presentinvention and a flow rate estimation device of the blood pump and ablood pump system to which the flow rate estimation method is applied.

FIG. 2 is a view for explaining the blood pump system according to theembodiment 1 of the present invention. The blood pump system 100Aincludes, as shown in FIG. 2, a blood pump (a objective blood pump) 10which discharges blood using a rotational force of the motor as adriving power source, an external controller 20 which controls anoperation of the objective blood pump 10, and a flow rate estimationdevice 30A of the blood pump for performing the flow rate estimation ofthe objective blood pump 10.

The external controller 20 includes a drive control part (not shown inthe drawing) for driving the objective blood pump 10, and a circulationliquid control part (not shown in the drawing) for lubricating andcooling a mechanical seal part in the objective blood pump 10. Theexternal controller 20 further includes, in addition to these parts, arotational speed measuring part 21 for measuring a rotational speed N ofthe motor, and a consumption current measuring part 22 for measuring aconsumption current I of the motor.

Here, in the blood pump system 100A according to the embodiment 1, theexternal controller 20 and the flow rate estimation device 30A of theblood pump are constituted as separate bodies from each other. However,the present invention is not limited to such a constitution and theexternal controller may have a flow rate estimation function of theblood pump (indicated by numeral 20A in FIG. 2).

The flow rate estimation device 30A of the blood pump includes anattribute data input part 32 for inputting attribute data of a testliquid or blood of a patient, a general flow rate estimation formulastoring part 33 which stores a general flow rate estimation formulawhich is formed based on the rotational speed of the motor, theconsumption current of the motor, the attribute data of the test liquid,and the flow rate of the blood pump and includes a correction term, aflow rate estimation formula forming part 34 which forms a flowrateestimation formula on the objective blood pump 10 by substitutingmeasured data on the rotational speed N₀ of the motor, the consumptioncurrent I₀ of the motor, the attribute data Z₀ of the blood of thepatient, and the flow rate Q₀ of the blood pump into the correctionterm, a flow rate estimation formula storing part 35 which stores theflow rate estimation formula formed by the flow rate estimation formulaforming part 34, a flow rate estimation part 36 which estimates the flowrate Q of the blood pump based on the flow rate estimation formulastored in the flow rate estimation formula storing part 35 using therotational speed N of the motor, the consumption current I of the motor,and the attribute data Z of the blood of the patient, and a control part31 which controls these parts. Further, the flow rate estimation device30A includes a connection part (not shown in the drawing), whichconnects the flow rate estimation device 30A with a blood flow meter 50which measures the flow rate of the objective blood pump 10.

Here, the flow rate estimation device 30A of the blood pump according tothe embodiment 1 includes the flow rate estimation formula forming part34 and the flow rate estimation formula storing part 35. However, thepresent invention is not limited to such a constitution, and the flowrate estimation device 30A may also include a flow rate estimationdevice of the blood pump which is provided with neither the flow rateestimation formula forming part 34 nor the flow rate estimation formulastoring part 35. In this case, the flow rate estimation part 36 formsthe flow rate estimation formula of the objective blood pump 10 based onthe general flow rate estimation formula which includes the correctionterm stored in the general flow rate estimation formula storing part 33and the measured data consisting of the measured rotational speed N₀ ofthe motor, the measured consumption current I₀ of the motor, themeasured attribute data Z₀ of the blood of the patient, and the flowrate Q₀ of the blood pump, for every time the flow rate estimation isperformed, and estimates the flow rate Q of the blood pump in theobjective blood pump 10 based on the flow rate estimation formula of theobjective blood pump 10. Here, in this case, the flow rate estimationdevice 30A may include a measured data storing part which stores theabove-mentioned measured data.

FIG. 3 is a view for explaining the flow rate estimation method of theblood pump according to the embodiment 1. The flow rate estimationmethod of the blood pump according to the embodiment 1 is constitutedof, as shown in FIG. 3, a first step and a second step.

(First Step)

The first step is constituted of a step in which the general flow rateestimation formula including the correction term is formed and a step inwhich the flow rate estimation formula of the objective blood pump 10 isformed.

Out of these steps, the step for forming the general flow rateestimation formula including the correction term is a step in which theplurality of blood pumps having the same standard and specification asthe objective blood pump 10 is prepared and flow rates of the bloodpumps are measured using flow meters (not shown in the drawing in FIG.2) when rotational speeds of the motors, consumption currents of themotors of the plurality of respective blood pumps and the attribute dataof the test liquid are respectively changed, and the general flow rateestimation formula including the correction term on which the individualdifference among the plurality of blood pumps is reflected is formedbased on the measured data.

As the test liquid, for example, water or a mixed solution of water andglycerin which is adjusted to a plurality of viscosities are used. Asthe attribute data of the test liquid, the viscosity μ and the density ρare used.

Further, the step for forming the flow rate estimation formula of theobjective blood pump 10 is a step in which a rotational speed N₀ of themotor, a consumption current I₀ of the motor of the objective blood pump10 implanted inside the body of the patient and the attribute data Z₀ ofthe blood of the patient are measured (at least one time) and, at thesame time, a flow rate Q₀ of the blood pump at this point of time ismeasured using the blood flow meter 50, the obtained measured data issubstituted into the correction term, whereby the flow rate estimationformula of the objective blood pump 10 is formed based on the generalflow rate estimation information. As the attribute data of the blood ofthe patient, the viscosity μ and the density ρ are used.

Among these steps, the step for forming the general flow rate estimationformula is usually collectively performed using a plurality of bloodpumps before shipping the objective blood pump 10.

Further, among these steps, the step for forming the flow rateestimation formula of the objective blood pump 10 is performed using theobjective blood pump 10 after implanting the objective blood pump 10inside the body of the patient.

(Step for Forming General Flow Rate Estimation Formula IncludingCorrection Term in First Step)

This step is a step in which a plurality of blood pumps is prepared, theflow rates of the blood pumps are measured using a flow meter (a flowmeter for industrial use or the like) when the rotational speeds of themotors and the consumption currents of the motors of the plurality ofrespective blood pumps, and the attribute data of the test liquid arerespectively changed, and the general flow rate estimation formulaincluding the correction term is formed based on the measured values.

FIG. 4 is a view which shows a relationship between a flow coefficient φobtained by standardizing the flow rate Q of the blood pump of the bloodpump system according to the embodiment 1 (=the flow rate Q of the bloodpump/(the flow path area A the impeller peripheral speed u)) and aconverted current ι obtained by standardizing the consumption current Iof the motor (=consumption current I of the motor/(density ρ of the testliquid×the angular velocity ω²)) for every viscosity μ of the testliquid (0.7 cP, 2.5 cP, 3.5 cP, 4.5 cP) and the rotational speed N ofthe motor (1000 rpm, 1400 rpm, 1800 rpm, 2200 rpm).

In the blood pump system 100A, as shown in FIG. 4, the flow coefficientφ and the converted current ι have an approximately linear relationship,and hence, it is possible to form a relationship formula (1) for everyrotational speed N of the motor by approximating the linear relationshipto a linear equation based on least square. The respective coefficientshere can be expressed as functions of the viscosity μ of the testliquid.

ι=(C·μ+D)φ+(E·μ+F)  (1)

Here, the coefficients C, D, E, and F can be expressed as functions ofthe rotational speed N of the motor. For example, the coefficients C, D,E, and F can be expressed as following functions.

C(N)=−1.12×10⁻¹¹ N ³+4.83×10⁻⁸ N ²−6.32×10⁻⁵ N+2.76×10⁻²

D(N)=6.57×10⁻⁵ N−9.39×10⁻³

E(N)=8.85×10⁻⁸ N+6.34×10⁻⁴

F(N)=2.00×10⁻⁹ N ²−8.85×10⁻⁶ N+1.38×10⁻²

Then, by developing the relationship formula (1), it is possible toobtain a basic estimation formula (2) described below.

Q=[I×10⁶/ρω²−(E(N)μ+F(N))]·[Au/(C(N)μ+D(N))]  (2)

FIG. 5 is a view showing the difference between the objective blood pumpand the arbitrary blood pump in the consumption current of the motor forevery rotational speed of the motor when the flow rate of the blood pumpis changed. As shown in FIG. 5, it is understood that the differencebetween the objective blood pump 10 and the arbitrary blood pump in theconsumption current of the motor is substantially fixed irrespective ofthe flow rate of the objective blood pump 10 at any rotational speed.

FIG. 6 is a view showing the difference (ratio) between the objectiveblood pump and the arbitrary blood pump in the consumption current ofthe motor when the rotational speed of the motor is changed. As shown inFIG. 6, it is understood that the difference (ratio) between theobjective blood pump 10 and the arbitrary blood pump in the consumptioncurrent of the motor is substantially fixed irrespective of therotational speed of the motor.

From these findings, it is understood that the flow rate Q of the bloodpump assumes a value which is offset by a predetermined value from aflow rate of the arbitrary blood pump irrespective of the rotationalspeed of the motor and the consumption current of the motor.Accordingly, by measuring this offset quantity using the objective bloodpump 10 and by adding the correction corresponding to the offsetquantity to the estimation result obtained from the basic estimationformula (2), it is possible to obtain the more accurate result of flowrate estimation in the objective blood pump 10. Accordingly, tofacilitate the later correction treatment in the step for forming theflow rate estimation formula of the objective blood pump, the followinggeneral flow rate estimation formula (3) which incorporates a correctionterm in the basic estimation formula (2) is formed.

Q={I×10⁶/ρω²−[E(N)μ+F(N)+((i*−A(μ*)φ*)−B(μ*))/B(μ*)×(E(N)μ+F(N))}·[Au/(C(N)μ+D(N))]  (3)

Here, i*, μ*, φ* are variable terms into which measured data i₀, μ₀, φ₀which are measured in the later step are inserted.

In the blood pump system 100A, the general flow rate estimation formula(3) including the correction term which is formed in this manner may bestored in the general flow rate estimation formula storing part 33.

(Step for Forming the Flow Rate Estimation Formula of Objective BloodPump in First Step)

This step is a step in which the rotational speed of the motor and theconsumption current of the motor of the objective blood pump 10implanted inside the body of the patient and the attribute data of theblood of the patient are measured and, at the same time, the flow rateof the blood pump is measured using the blood flow meter 50, and theflowrate estimation formula of the objective blood pump is formed fromthe general flow rate estimation formula (3) by substituting theobtained data into the correction term.

As has been described above, the flow rate Q of the blood pump assumes avalue which is offset by the predetermined value from the flow rate ofthe arbitrary blood pump irrespective of the rotational speed of themotor and the consumption current of the motor. Accordingly, therotational speed N₀ of the motor and the consumption current I₀ of themotor of the objective blood pump 10 implanted inside the body of thepatient, and the attribute data Z₀ of the blood of the patient (at leastone time) are measured, and at the same time the flow rate Q₀ of theblood pump at this point of time is measured using the blood flow meter50, whereby the flow rate estimation formula (4) of the objective bloodpump 10 is formed by substituting the obtained measured data into thecorrection term of the general flow rate estimation formula (3).

Q={I×10⁶/ρω² −[E(N)μ+F(N)+((i ₀−A(μ₀)φ₀)−B(μ₀))/B(μ₀)×(E(N)μ+F(N))]}·[Au/(C(N)μ+D(N))]  (4)

The formation of the flow rate estimation formula (4) of the objectiveblood pump 10 is performed by the flow rate estimation formula formingpart 34. Then, the obtained flow rate estimation formula (4) is storedin a flow rate estimation formula storing part 35.

(Second Step)

The second step is a step in which the rotational speed N of the motorand the consumption current I of the motor of the objective blood pump10 implanted inside the body of the patient, and the attribute data Z ofthe blood of the patient are measured, and the flow rate Q of the bloodpump is estimated based on the flow rate estimation formula (4) which isstored in the flow rate estimation formula storing part 35 and thesevalues N, I and Z. As the attribute data of the blood of the patient,the viscosity μ and the density ρ are used.

Here, with respect to the rotational speed N of the motor and theconsumption current I of the motor, the measured data is obtained byperforming the automatic measurement every time the flow rate estimationis performed, while with respect to the attribute data Z (μ, φ) of theblood of the patient, the measured data is obtained by inputting theattribute data using the attribute data input part 32.

FIG. 7 is a view showing the difference between the estimated flow rateof the objective blood pump obtained by estimation using the flow rateestimation formula (4) and the measured flow rate obtained by actuallymeasuring the flow rate using the flow meter under proper conditions.Such a difference is, as shown in FIG. 7, when the flow rate of theblood pump is within a range of 10 litters/min or less, set to a valuesmaller than a target value (±1 litter/min) which is considered as anallowable range clinically. It is confirmed that the flow rate of theblood pump can be accurately estimated according to the flow rateestimation method of the blood pump of the embodiment 1.

Although the flow rate estimation method of the blood pump according tothe embodiment 1 has been explained heretofore, by using the flow rateestimation method of the blood pump according to the embodiment 1, inthe first step, the flow rate estimation formula (4) is formed withrespect to the objective blood pump 10 on which the flow rate estimationis performed, and in the second step, the flow rate estimation isperformed with respect to the objective blood pump 10 based on the flowrate estimation formula (4), and hence, the deterioration of theaccuracy of the result of the flow rate estimation due to the individualdifference of the property of the blood pump can be effectivelysuppressed.

Further, according to the flow rate estimation method of a blood pump ofthe embodiment 1, the flow rate estimation formula (4) is formed byusing the objective blood pump 10 which is implanted inside the body ofthe patient, and hence, it is possible to form the flow rate estimationformula (4) with respect to the objective blood pump 10 under theenvironment in which the blood pump 10 is actually used whereby thedeterioration of the accuracy of the flow rate estimation resultattributed to the difference of the environment in which the blood pumpis used can be effectively suppressed.

Further, according to the flow rate estimation method of a blood pump ofthe embodiment 1, the flow rate estimation formula (4) is formed usingthe objective blood pump 10 implanted inside the body of the patientand, thereafter, the flow rate estimation of the objective blood pump 10can be performed based on the flowrate estimation formula (4), andhence, it is possible to effectively prevent the deterioration ofaccuracy of the flow rate estimation result attributed to the change ofthe property of the blood pump along with a lapse of time.

Further, according to the flow rate estimation method of a blood pump ofthe embodiment 1, the formation of the flow rate estimation formula (4)which is originally cumbersome and time-consuming is divided into thestep which forms the general flow rate estimation formula (3) includingthe correction term and the step which forms the flow rate estimationformula (4) on the objective blood pump by substituting the measureddata obtained for every objective blood pump into the correction term,wherein among these steps, the former step which is originallycumbersome and time-consuming is performed preliminarily using aplurality of blood pumps, and the latter step which is relatively lesstime-consuming is performed using the objective blood pump whereby it ispossible to further easily form the flow rate estimation formula (4) asa whole.

In the flow rate estimation method of a blood pump according to theembodiment 1, in estimating the flow rate of the blood pump in step 2,when it is possible to measure the flow rate of the objective blood pump10 using the blood flow meter 50, the flow rate of the objective bloodpump 10 is measured using the flow meter 50 at the time of performingthe second step, and hence, the flow rate estimation formula (4) can bealways updated to the newest flow rate estimation formula (4).Accordingly, even when the property of the blood pump is changed alongwith a lapse of time, the flow rate estimation of the blood pump can beperformed using the newest flow rate estimation formula (4), whereby itis possible to further effectively suppress the deterioration ofaccuracy of the result of the flow rate estimation attributed to thechange of the property of the blood pump along with a lapse of time.

In the flow rate estimation method of a blood pump according to theembodiment 1, as the blood flow meter 50, a blood flow meter based on athermodilution method is used. In this case, by adjusting the rotationalspeed of the motor of the objective blood pump 10 such that the wholeblood in the body circulatory system passes through the objective bloodpump 10 by reference to a blood monitor, an ultrasonic diagnosis deviceor the like, the blood flow rate obtained by blood flow meter 50 becomessubstantially equal to the blood flow rate of the objective blood pump10, and hence, it is possible to perform the flow rate estimation of theblood pump with higher accuracy. Here, in performing the measurement ofthe flow rate using the blood flow meter 50, it is necessary to implanta catheter inside the body of the patient. However, the implanting ofthe catheter for a certain period after an operation to implant theblood pump is usually performed, and hence, it isn't further invasive tothe patient.

In the flow rate estimation method of a blood pump according to theembodiment 1, viscosity and density are used as the attribute data ofthe test liquid and the blood of the patient. Accordingly, compared to acase in which either one of viscosity or density is adopted, it ispossible to perform the flow rate estimation of the blood pump withhigher accuracy.

In the flow rate estimation method of a blood pump according to theembodiment 1, in place of measuring viscosity and density of the bloodof the patient in the second step, a hematocrit value may be measured,and the flow rate of the blood pump may be estimated using convertedviscosity and converted density obtained by converting the hematocritvalue. By adopting such a method, it is possible to perform the flowrate estimation of the blood pump using a simple method which measuresonly the hematocrit value without measuring viscosity and density of theblood of the patient.

FIG. 8 is a view showing a relationship between the hematocrit value ofthe blood and the viscosity of the blood, while FIG. 9 is a view showinga relationship between the hematocrit value of the blood and the densityof the blood. As shown in FIG. 8 and FIG. 9, between the hematocritvalue of the blood and the viscosity and the density of the blood, astrong correlation exists. That is, also with respect to the blood ofthe patient, there exists a strong correlation between the hematocritvalue Ht of the blood of the patient and the viscosity μ and the densityρ of the blood of the patient, and hence, in place of measuring theviscosity μ and the density ρ of the blood of the patient, the viscosityμ and the density ρ of the blood of the patient can be obtained bymeasuring the hematocrit value Ht of the blood of the patient and byconverting the hematocrit value Ht of the blood of the patient to theviscosity μ and the density ρ of the blood of the patient.

As has been explained above, the flow rate estimation method of a bloodpump according to the embodiment 1 is an excellent flow rate estimationmethod of a blood pump, which can effectively suppress the deteriorationof the accuracy of the flow rate estimation result attributed to theindividual difference of the blood pump, the dependency on usageenvironment, or the change along with a lapse of time. Accordingly, withthe use of such an excellent flow rate estimation method of a bloodpump, it is possible to perform treatment using the implantable bloodpump more properly.

Further, the flow rate estimation device 30A of a blood pump accordingto the embodiment 1 can perform the flow rate estimation of the bloodpump using the excellent flow rate estimation method of a blood pump,which can effectively suppress the deterioration of the accuracy of theflow rate estimation result attributed to the individual difference, thedependency on usage environment, or the change along with a lapse oftime of the blood pump described above. Accordingly, with the use ofsuch an excellent flow rate estimation device 30A of the blood pump, itis possible to perform treatment using the implantable blood pump moreproperly.

Further, the blood pump system 100A according to the embodiment 1 is ablood pump system provided with the excellent flow rate estimationdevice 30A of a blood pump, which can effectively suppress thedeterioration of the accuracy of the flow rate estimation resultattributed to the individual difference, the dependency on usageenvironment, or the change along with a lapse of time of the blood pumpdescribed above. Accordingly, with the use of such an excellent bloodpump system 100A, it is possible to perform treatment using theimplantable blood pump more properly.

Still further, the general flow rate estimation formula to be stored inthe general flow rate estimation formula storing part 33 and the flowrate estimation formula of the objective blood pump 10 to be stored inthe flow rate estimation formula storing part 35 in the flow rateestimation device 30A of the blood pump according to the embodiment 1may be stored in a predetermined storage medium (for example, a CD-ROM).In this case, by allowing a computer system to read the flow rateestimation formulae stored in the storage medium, it is possible to usethe computer system as the flow rate estimation device 30A of the bloodpump. Accordingly, with the use of such a storage medium, it is possibleto perform the treatment using the implantable blood pump more properly.

EMBODIMENT 2

Embodiment 2 is an embodiment with respect to a flow rate estimationmethod of a blood pump described in claim 5 of the present invention anda flow rate estimation device of a blood pump and a blood pump system towhich the flow rate estimation method of a blood pump is applied.

FIG. 10 is a view for explaining a blood pump system according to theembodiment 2 of the present invention. The blood pump system 100B (andthe flow rate estimation device 30B of the blood pump) according to theembodiment 2 has, as shown in FIG. 10, the same constitution as theblood pump system 100A (and the flow rate estimation device 30A of theblood pump) according to the embodiment 1 except for the point that theembodiment 2 is not provided with the connection part with the bloodflow meter.

FIG. 11 is a view for explaining a flow rate estimation method of theblood pump according to the embodiment 2. The flow rate estimationmethod of the blood pump according to the embodiment 2 is constituted ofa first step and a second step as shown in FIG. 11.

(First Step)

The first step is constituted of a step in which the general flow rateestimation formula including the correction term is formed and a step inwhich the flow rate estimation formula of the objective blood pump 10 isformed.

Out of these steps, the step which forms the general flow rateestimation formula including the correction term is a step in which theplurality of blood pumps having the same standard and specification asthe objective blood pump 10 is prepared and flow rates of the bloodpumps are measured using flow meters (such as flow meters for industrialuse) when rotational speeds of the motors, consumption currents of themotors of the plurality of respective blood pumps and the attribute dataof the test liquid are respectively changed, whereby the general flowrate estimation formula including the correction term is formed.

As the test liquid, for example, water and a mixed solution of water andglycerin which is adjusted to a plurality of viscosities are used. Asthe attribute data of the test liquid, the viscosity μ and the density ρare used. That is, the test liquid is used in the same manner as theflow estimation method of the blood pump according to the embodiment 1.

Further, the step for forming the flow rate estimation formula of theobjective blood pump 10 is a step in which a rotational speed of themotor, a consumption current of the motor of the objective blood pump10, and the attribute data of the test liquid are measured and, at thesame time, a flow rate of the blood pump is measured using the flowmeter, and the flow rate estimation formula of the objective blood pump10 is formed based on the general flow rate estimation information bysubstituting the obtained data into the correction term. As the testliquid, for example, water or a mixed solution of water and glycerin isused. It is particularly preferable to use a solution which is adjustedto have the viscosity substantially equal to the viscosity of the blood.As the attribute data of the test liquid, the viscosity μ and thedensity ρ are used.

Among these steps, the step for forming the general flow rate estimationformula including the correction term is, in the same manner as theembodiment 1, collectively performed using a plurality of blood pumpsbefore shipping the objective blood pump 10.

Further, among these steps, the step for forming the flow rateestimation formula of the objective blood pump 10 is performed,different from the embodiment 1, using the objective blood pump 10before shipping the objective blood pump 10.

(Second Step)

The second step is a step in which the rotational speed N of the motorand the consumption current I of the motor of the objective blood pump10 implanted inside the body of the patient, and the attribute data Z ofthe blood of the patient are measured, and the flow rate Q of the bloodpump of the objective blood pump 10 is estimated based on the flow rateestimation formula of the objective blood pump 10 which is formedpreviously and these values N, I and Z. The second step is substantiallyequal to the second step of the embodiment 1. As the attribute data ofthe blood of the patient, the viscosity μ and the density ρ are used.

The second step is performed after implanting the objective blood pump10 inside the body of the patient in the same manner as the embodiment1.

In this manner, according to the flow rate estimation method of theblood pump of the embodiment 2, in the same manner as the embodiment 1,in the first step, the flow rate estimation formula is formed withrespect to the objective blood pump 10 on which the flow rate estimationis performed, while in the second step, the flow rate estimation isperformed with respect to the objective blood pump 10 based on this flowrate estimation formula, and hence, it is possible to effectivelysuppress the deterioration of the accuracy of the flow rate estimationresult attributed to the individual difference of the property of theblood pump.

Further, according to the flow rate estimation method of the blood pumpof the embodiment 2, different from the case of the flow rate estimationmethod of a blood pump according to the embodiment 1, the flow rateestimation formula is formed using the test liquid, and hence, it ispossible to finish the cumbersome and time-consuming first step beforeshipping.

Further, since the cumbersome and time-consuming first step can beperformed before implanting the objective blood pump 10 inside the bodyof the patient, a burden imposed on the patient is not increased.

Still further, by performing the formation of the flow rate estimationformula for every objective blood pump, it may be possible to performthe flow rate estimation with respect to the objective blood pump withhigher accuracy immediately after implanting the objective blood pumpinside the body of the patient.

In the flow rate estimation method of a blood pump according to theembodiment 2, the originally cumbersome and time-consuming formation ofthe flow rate estimation formula in the first step is divided into thestep which forms the general flow rate estimation formula including thecorrection term and the step which forms the flow rate estimationformula with respect to the objective blood pump, and the latter step isperformed before shipping, and hence, compared to the flow rateestimation method of the blood pump according to the embodiment 1, theflow rate estimation formula can be further easily formed as a whole.

As has been explained above, the flow rate estimation method of a bloodpump according to the embodiment 2 is an excellent flow rate estimationmethod of a blood pump, which can effectively suppress the deteriorationof the accuracy of the result of flow rate estimation attributed to theindividual difference of the blood pump as mentioned above. Accordingly,also with the use of such an excellent flow rate estimation method of ablood pump, it is possible to perform treatment using the implantableblood pump more properly.

Further, the flow rate estimation device 30B of a blood pump accordingto the embodiment 2 can perform the flow rate estimation of the bloodpump using the excellent flow rate estimation method of a blood pump,which can effectively suppress the deterioration of the accuracy of theresult of the flow rate estimation attributed to the individualdifference of the blood pump as described above. Accordingly, also withthe use of such an excellent flow rate estimation device 30B of theblood pump, it is possible to perform treatment using the implantableblood pump more properly.

Further, the blood pump system 100B according to the embodiment 2 is ablood pump system provided with the excellent flow rate estimationdevice 30B of the blood pump, which can effectively suppress thedeterioration of the accuracy of the flow rate estimation resultattributed to the individual difference of the blood pump as describedabove. Accordingly, also with the use of such an excellent blood pumpsystem 100B, it is possible to perform treatment using the implantableblood pump more properly.

Still further, the general flow rate estimation formula to be stored inthe general flow rate estimation formula storing part 33 and the flowrate estimation formula of the objective blood pump to be stored in theflow rate estimation formula storing part 35 in the flow rate estimationdevice 30B of the blood pump according to the embodiment 2 may be storedin the predetermined storage medium (for example, a CD-ROM). In thiscase, by allowing a computer system to read the flow rate estimationformulae stored in the storage medium, it is possible to use thecomputer system as the flow rate estimation device 30B of the bloodpump. Accordingly, with the use of such a storage medium, it is possibleto perform the treatment using the implantable blood pump more properly.

Here, in the blood pump system 100B (and the flow rate estimation device30B of the blood pump) according to the embodiment 2, the general flowrate estimation formula storing part 33 and the flow rate estimationformula forming part 34 may be omitted. This is because that therespective parts are provided for performing functions necessary inperforming the first step before shipping, and hence, these parts arenot prerequisite in the blood pump system 100B (and the flow rateestimation device 30B of the blood pump) after shipping.

EMBODIMENT 3

An embodiment 3 is an embodiment with respect to a flow rate estimationmethod of a blood pump described in claim 4 of the present invention anda flow rate estimation device of a blood pump and a blood pump system towhich the flow rate estimation method of a blood pump is applied.

FIG. 12 is a view for explaining a blood pump system according to theembodiment 3 of the present invention. The blood pump system 100C (andthe flow rate estimation device 30C of the blood pump) according to theembodiment 3 have, as shown in FIG. 12, the same constitution as theblood pump system 100B (and the flow rate estimation device 30B of theblood pump) according to the embodiment 2 except for the point that theembodiment 3 is not provided with the general flow rate estimationformula storing part 33 and the flow rate estimation forming part 34.

FIG. 13 is a view for explaining a flow rate estimation method of theblood pump according to the embodiment 3. The flow rate estimationmethod of the blood pump according to the embodiment 3 is constituted ofa first step and a second step as shown in FIG. 13.

(First Step)

The first step is a step in which the flow rate of the blood pump whenthe rotational speed of the motor and the consumption current of themotor of the objective blood pump 10, and the attribute data of the testliquid are respectively changed is measured using the flow meter (suchas a flow meter for industrial use), and the flowrate estimationformula, which constitutes the flow rate estimation information whichdescribes the relationship among the rotational speed of the motor, theconsumption current of the motor and the flow rate of the blood pump ofthe objective blood pump 10, and the attribute data of the test liquid,is formed. As the test liquid, for example, water and a mixed solutionof water and glycerin which is adjusted to a plurality of viscositiesare used. As the attribute data of the test liquid, the viscosity μ andthe density ρ are used.

The first step is usually performed for every objective blood pumpbefore shipping the objective blood pump 10.

(Second Step)

The second step is a step in which the rotational speed N of the motorand the consumption current I of the motor of the objective blood pump10 implanted inside the body of the patient, and the attribute data Z ofthe blood of the patient are measured, and the flow rate Q of the bloodpump of the objective blood pump 10 is estimated based on the flow rateestimation formula and these values N, I and Z. As the attribute data ofthe blood of the patient, the viscosity μ and the density ρ are used.The second step is substantially equal to the second step of theembodiment 1 and the embodiment 2.

The second step is performed after implanting the objective blood pump10 inside the body of the patient.

In this manner, according to the flow rate estimation method of theblood pump of the embodiment 3, in the first step, the flow rateestimation formula is determined with respect to the objective bloodpump 10 on which the flow rate estimation is performed, while in thesecond step, the flow rate estimation is performed with respect to theobjective blood pump 10 based on this flow rate estimation formula, andhence, it is possible to effectively suppress the deterioration of theaccuracy of the flow rate estimation result attributed to the individualdifference of the property of the blood pump.

The step which forms the flow rate estimation formula in the first stepis the originally cumbersome and time-consuming step. This is because todetermine the flow rate estimation formula, it is necessary to measurethe flow rate by changing the rotational speed of the motor, theconsumption current of the motor and the attribute data of the testliquid respectively.

However, in the flow rate estimation method of the blood pump accordingto the embodiment 3, the flow rate estimation formula is formed usingthe test liquid, and hence, it is possible to finish such a cumbersomeand time-consuming first step before shipping.

Further, since the cumbersome and time-consuming first step can beperformed before implanting the objective blood pump 10 inside the bodyof the patient, a burden imposed on the patient is not increased.

Still further, by performing the formation of the flow rate estimationformula for every objective blood pump, it may be possible to performthe flow rate estimation with respect to the objective blood pump withhigher accuracy immediately after implanting the objective blood pumpinside the body of the patient.

As has been explained above, the flow rate estimation method of a bloodpump according to the embodiment 3 is an excellent flow rate estimationmethod of a blood pump, which can effectively suppress the deteriorationof the accuracy of the flow rate estimation result attributed to theindividual difference of the blood pump as mentioned above. Accordingly,also with the use of such an excellent flow rate estimation method of ablood pump, it becomes possible to perform treatment using theimplantable blood pump more properly.

Further, the flow rate estimation device 30C of a blood pump accordingto the embodiment 3 can perform the flow rate estimation of the bloodpump using the excellent flow rate estimation method of a blood pump,which can effectively suppress the deterioration of the accuracy of theflow rate estimation result attributed to the individual difference ofthe blood pump as described above. Accordingly, also with the use ofsuch an excellent flow rate estimation device 30C of the blood pump, itbecomes possible to perform treatment using the implantable blood pumpmore properly.

Further, the blood pump system 100C according to the embodiment 3 is ablood pump system provided with the excellent flow rate estimationdevice 30C of the blood pump, which can effectively suppress thedeterioration of the accuracy of the flow rate estimation resultattributed to the individual difference of the blood pump as describedabove. Accordingly, with the use of such an excellent blood pump system100C, it becomes possible to perform treatment using the implantableblood pump more properly.

Still further, the flow rate estimation formula to be stored in the flowrate estimation formula storing part 35 in the flow rate estimationdevice 30C of the blood pump according to the embodiment 3 may be storedin the predetermined storage medium (for example, a CD-ROM). In thiscase, by allowing a computer system to read the flow rate estimationformula stored in the storage medium, it becomes possible to use thecomputer system as the flow rate estimation device 30C of the bloodpump. Accordingly, with the use of such a storage medium, it is possibleto perform the treatment using the implantable blood pump more properly.

Although the flow rate estimation method of a blood pump and the bloodpump system of the present invention have been explained in conjunctionwith the above-mentioned respective embodiments, the present inventionis not limited to such embodiments and various modifications areconceivable as exemplified below.

(a) In the above-mentioned respective embodiments, the flow rateestimation formula (and the general flow rate estimation formula) is/areused as the flow rate estimation information. However, the presentinvention is not limited to these embodiments and a flow rate estimationtable (and a general flow rate estimation table) may be used as flowrate estimation information so as to obtain the substantially equaladvantageous effects.

(b) In the above-mentioned respective embodiments, the blood pump whichincludes the mechanical seal part is used as the blood pump. However,the present invention is not limited to these embodiments and thepresent invention can obtain the substantially equal advantageouseffects even when other blood pumps which may have the individualdifference, the dependency on usage environment or a change along with alapse of time is used.

(c) In the above-mentioned embodiment 3, the blood pump which includesthe DC motor is used as the blood pump. However, even when the bloodpump which uses as a motor in place of the DC motor is used, it ispossible to obtain advantageous effects substantially equal advantageouseffects obtained by the embodiment 3.

(d) In the above-mentioned respective embodiments, a centrifugal pump isused as a blood pump. However, the present invention is not limited tothe respective embodiments and even when other blood pump (for example,an axial pump) is used, the present invention can obtain thesubstantially equal advantageous effects.

(e) In the above-mentioned embodiment 1, a blood flow meter based on thethermal dilution method is used as the blood flow meter. However, inplace of this blood flow meter, other blood flow meter (for example, ablood flow meter based on a dye dilution method, an electromagneticblood flow meter, an ultrasonic blood flow meter, a blood flow meterbased on a transesophageal echocardiography, a blood flow meter based ona transthoracic echocardiography or a blood flow meter based on anelectric impedance method) may be used so as to obtain the substantiallysame advantageous effects as the embodiment 1.

(f) As the flow meter for industrial use which is used in theabove-mentioned respective embodiments, it is possible to use anultrasonic flow meter, an electromagnetic flow meter and other variousflow meters for industrial use.

EXPLANATION OF SYMBOLS

10: blood pump (objective blood pump), 11: drive part, 12: pump part,13: impeller, 14: pump casing, 15: inlet port, 16: outlet port, 17:mechanical seal part, 20: external controller, 21: rotational speedmeasuring part, 22: consumption current measuring part, 30A, 30B, 30C:flow rate estimation device of blood pump, 31: control part, 32:attribute data input part, 33: general flow rate estimation formulastoring part, 34: flow rate estimation formula forming part, 35: flowrate estimation formula storing part, 36: flow rate estimation part, 50:blood flow meter, 100A, 100B, 100C: blood pump system, 901: blood pumpsystem, 905: blood pump, 921: impeller, 934: motor, 955: sensor circuit,957: blood parameter input part, 958: discharge flow rate arithmeticcalculation part, 960:viscosity/rotational-speed/motor-current/discharge-flow-rate relevantdata storing part

1. A method of estimating a flow rate Q of an objective blood pump,which discharges blood using a rotational force of a motor as a drivingpower source, based on a rotational speed N of the motor, a consumptioncurrent I of the motor, and attribute data Z of blood of a patient, thecomprising: a first step of obtaining flow rate estimation informationwhich describes a relationship among the rotational speed of the motor,the consumption current of the motor and the flow rate of the objectiveblood pump, and the attribute data of a test liquid or blood; and asecond step of estimating the flow rate Q of the objective blood pumpbased on the flow rate estimation information and the values of N, I andZ which are obtained by measuring the rotational speed N and theconsumption current I of the motor in the objective blood pump, which isimplanted inside the body of the patient, and the attribute data Z ofthe blood of the patient.
 2. The method according to claim 1, whereinthe flow rate estimation information is a flow rate estimation formula.3. The method according to claim 1, wherein the flow rate estimationinformation is a flow rate estimation table.
 4. The method according toclaim 1, wherein the first step is a step which forms the flow rateestimation information by measuring the flow rate of the objective bloodpump using a blood flow meter when the rotational speed and theconsumption current of the motor in the objective blood pump, and theattribute data of the test liquid are respectively changed.
 5. Themethod according to claim 1, wherein the first step includes: a stepwhich forms general flow rate estimation information includingcorrection information by measuring flow rates of a plurality of bloodpumps using a blood flow meter when rotational speeds and consumptioncurrents of motors in the respective blood pumps, and the attribute dataof the test liquid are respectively changed, and a step in which therotational speed and the consumption current of the motor in theobjective blood pump and the attribute data of the test liquid aremeasured, the flow rate of the objective blood pump is measured using ablood flow meter, and the flow rate estimation information on theobjective blood pump is formed based on the general flow rate estimationinformation by substituting the obtained measured data into thecorrection information.
 6. The method according to claim 1, wherein thefirst step includes: a step which forms general flow rate estimationinformation including correction information by measuring flow rates ofa plurality of blood pumps using a blood flow meter when rotationalspeeds and consumption currents of motors in the respective blood pumps,and the attribute data of the test liquid are respectively changed, anda step in which the rotational speed and the consumption current of themotor in the objective blood pump which is implanted inside the body ofthe patient, and the attribute data of the blood of the patient aremeasured, the flow rate of the objective blood pump is measured using ablood flow meter, and the flow rate estimation information on theobjective blood pump is formed based on the general flow rate estimationinformation by substituting the obtained measured data into thecorrection information.
 7. The method according to claim 6, wherein theblood flow meter is a blood flow meter based on a thermodilution method,a blood flow meter based on a dye dilution method, an electromagneticblood flow meter, an ultrasonic blood flow meter, a blood flow meterbased on a transesophageal echocardiography, a blood flow meter based ona transthoracic echocardiography or a blood flow meter based on anelectric impedance method.
 8. (canceled)
 9. The method according toclaim 5, wherein the motor is a DC motor.
 10. The method according toclaim 1, wherein the attribute data of the test liquid or the blood ofthe patient comprises viscosity and density.
 11. The method according toclaim 1, wherein the attribute data Z of the blood of the patientcomprises converted viscosity and converted density which are obtainedby conversion of based on a hematocrit value of the blood of thepatient.
 12. The method according to claim 1, wherein the blood pump hasa mechanical seal part for performing shaft-sealing of a rotationalshaft of the motor.
 13. A method of estimating a flow rate Q of anobjective blood pump, which discharges blood using a rotational force ofa motor as a driving power source, based on a rotational speed N of themotor, a consumption current I of the motor, and attribute data Z of theblood of a patient, wherein the rotational speed N and the consumptioncurrent I of the motor of the objective blood pump which is implantedinside the body of the patient, and the attribute data Z of the blood ofthe patient are measured, and the flow rate Q of the objective bloodpump is estimated based on preliminarily formed flow rate estimationinformation on the objective blood pump and the values of N, I and Z.14. A flow rate estimation device of a blood pump for estimating a flowrate of the blood pump by the method according to claim 1, wherein theflow rate estimation device comprises: an attribute data input part forinputting the attribute data Z of the blood of the patient, a flow rateestimation information storing part for storing the flow rate estimationinformation on the objective blood pump, and a flow rate estimation partfor estimating the flow rate Q of the objective blood pump based on theflow rate estimation information stored in the flow rate estimationinformation storing part using the rotational speed N of the motor, theconsumption current I of the motor and the attribute data Z of the bloodof the patient.
 15. A blood pump system comprising: a blood pump fordischarging blood using a rotational force of a motor as a driving powersource, and an external controller for controlling an operation of theblood pump, wherein the blood pump system further includes the flow rateestimation device of the blood pump according to claim
 14. 16. A storagemedium for use with the flow rate estimation device of the blood pumpaccording to claim 14, wherein the storage medium stores the flow rateestimation information.
 17. The flow rate estimation device of the bloodpump according to claim 14, further comprising: a general flow rateestimation information storing part for storing general flow rateestimation information, which is formed based on the rotational speedand consumption current of the motor, the attribute data of the testliquid, and the flow rate of the blood pump and includes a correctionterm; and a flow rate estimation information forming part for formingthe flow rate estimation information on the objective blood pump bysubstituting measured data on a rotational speed N₀ and a consumptioncurrent I₀ of the motor, attribute data Z₀ of the blood of the patient,and a flow rate of Q₀ of the objective blood pump into the correctionterm.
 18. A storage medium for use with the flow rate estimation deviceof the blood pump according to claim 17, wherein the storage mediumstores the general flow rate estimation information including thecorrection-term.
 19. A flow rate estimation device of a blood pump forestimating a flow rate of the blood pump by the method according toclaim 13, wherein the flow rate estimation device comprises: anattribute data input part for inputting the attribute data Z of theblood of the patient, a flow rate estimation information storing partfor storing the flow rate estimation information on the objective bloodpump, and a flow rate estimation part for estimating the flow rate Q ofthe objective blood pump based on the flow rate estimation informationstored in the flow rate estimation information storing part using therotational speed N of the motor, the consumption current I of the motorand the attribute data Z of the blood of the patient.
 20. The methodaccording to claim 6, wherein in the motor is a DC motor.